JPS61224425A - Pattern formation of semiconductor device - Google Patents

Abstract

PURPOSE:To improve the lift-off process for forming a fine pattern on a semiconductor substrate by a method wherein a thin film is coated with a photoresist CONSTITUTION:A semiconductor substrate 100 is coated with e.g. silicon dioxide thin film 1 conforming to the pattern position of specified metallic layer and.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pattern forming method for a semiconductor device, and particularly to a pattern forming method using a lift-off method to form a wiring pattern for a semiconductor device.

[Technical background of the invention and its problems]

In semiconductor devices such as semiconductor integrated circuits, the degree of integration,
In order to improve electrical characteristics and the like, miniaturization of device dimensions is actively underway, and pattern dimensions have already reached the submicron range. In forming such a pattern, it is essential to faithfully transfer the pattern on the mask onto the semiconductor substrate, and wet etching, dry etching, lift-off, and the like are widely used for pattern formation.

The above wet etching method involves a large amount of side etching, and it is difficult to control the amount of side etching with good reproducibility, so there is a problem in forming patterns with high precision. There are drawbacks such as abnormal penetration of the etching solution into the interface between the material to be etched and the photoresist, which is often caused by poor adhesion between the etching material and the photoresist. Additionally, the dry etching method has advantages over the wet etching method, such as a smaller amount of side etching and less problems with adhesion between the material to be etched and the photoresist. This causes problems such as hardening of the photoresist or damage to the semiconductor during dry etching. Furthermore, when the photoresist is not cut vertically, there is a problem that the resist dimension gradually decreases due to film thinning during dry etching. In this way, both of the above etching methods cannot necessarily be said to be effective means for forming submicron patterns.

In contrast to the above, the lift-off method has the advantage of being able to faithfully transfer an open pattern of a photoresist as a metal pattern onto a semiconductor substrate, and is therefore widely used in forming sub-micron metal patterns. This is the second
As shown in the figure, if the photoresist layer 101 on the semiconductor substrate 100 is simply patterned and the metal layer 102 is simply deposited, the metal layer portion 1 deposited on the photoresist layer 1
02a and the metal layer portion 102b deposited on the semiconductor substrate are connected at the part indicated by the tip of the arrow, and by removing the photoresist layer, only the metal layer portion 102a deposited on the top surface is removed. Liftoff cannot be achieved. Both metal layers 102a are subjected to lift-off.

102b must be spatially separated.

Therefore, generally, as shown in FIG.
A spacer layer 103 for lift-off is provided between the photoresist layer 101 and the photoresist layer 101, and after making an opening in the photoresist layer 101, the metal layer on the photoresist layer 101 is etched using side etching when etching the spacer layer 103. This prevents contact between the metal layer 102a and the metal layer 102b on the semiconductor substrate 100.

In the conventional lift-off method described above, the spacer layer 103 remains on the semiconductor substrate 100 after lift-off, so depending on the type and thickness of the spacer layer, it may adversely affect the electrical characteristics of the device or post-processing. There is a drawback that it is difficult to control the side etching amount of the spacer layer, which causes a decrease in yield in the manufacture of semiconductor devices.

[Purpose of the invention]

One aspect of the present invention is to eliminate the above-mentioned drawbacks and improve the lift-off method for forming fine patterns on a semiconductor substrate.

[Summary of the invention]

In the method for forming a pattern of a semiconductor device of the present invention, a thin film is formed on a semiconductor substrate to be thicker than a metal layer to be provided thereon, and then a photoresist layer is deposited on the entire surface, and then the thin film is coated on the semiconductor substrate. forming an opening narrower than the width of the photoresist layer, removing the thin film using the photoresist layer as a mask, forming a metal layer, and then removing the metal layer on the photoresist layer together with the photoresist layer to remove the thin film. The feature is that a metal pattern is formed at the location where the metal is placed.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

A pattern forming method according to an embodiment is shown in FIGS. 1(a) to 1(e) in order of steps. In the figure, parts that are the same as in the prior art are designated by the same reference numerals, and explanations thereof will be omitted.

A thin film 1 of silicon dioxide, for example, is deposited on a semiconductor substrate 100 (FIG. a). This thin film is formed to be thicker than the metal layer of the wiring or electrode pattern that will be formed later.

Next, wet etching is performed so as to match the position of the metal layer pattern to be formed on the semiconductor substrate 100 and leave a thin film pattern la slightly wider than the width thereof, and then a photoresist layer 2 is applied to the entire surface. (Figure b)
).

Next, a predetermined opening 2a that is narrower than the width of the thin film pattern 1a is provided in the photoresist layer 2 on which the thin film pattern is formed, and the thin film pattern 1a is completely removed (Figure c). The cavity 2b having a convex cross-sectional shape is wide at the part in contact with the semiconductor substrate 100 and narrow at the upper part.
The shape is suitable for lift-off.

A metal layer 3 is then applied over the entire surface, for example by vapor deposition.

This metal layer 3 becomes a patterned metal layer 2a deposited on the semiconductor substrate 100 below by means of a metal layer 3b on the photoresist layer and an opening 2a in the photoresist layer (1
! Id).

Next, by removing the photoresist layer 2, the metal 1iJ3 on the photoresist layer deposited thereon is removed.
b is also removed, and a metal layer 3a having a predetermined pattern is deposited on the semiconductor substrate (FIG. e).

Although the above embodiments have been described in which patterning is performed on a semiconductor substrate, the present invention is equally effective in cases where an electrical insulating layer such as silicon nitride or other wiring pattern has already been formed on the semiconductor substrate. Further, although the SiO2 film is exemplified as the thin film, it goes without saying that other electrical insulating layers, metal films, etc. may also be used.

〔Effect of the invention〕

As described above, according to the present invention, the selectively formed thin film is removed before the metal layer is deposited, so that the electrical problems of the device, which occur when the thin film is on the semiconductor substrate as in the conventional method, are removed. It has the remarkable advantage of preventing adverse effects on properties and manufacturing processes. In addition, since a thin film of predetermined dimensions is first formed and the thin film is completely removed during lift-off, it solves the instability of the amount of side etching caused by liquid seepage due to poor adhesion between the thin film and photoresist. There is also the advantage of being able to do so. As described above, with the lift-off method according to the present invention, submicron patterns can be formed stably and with good reproducibility, so that the manufacturing yield of semiconductor devices can be significantly improved.

[Brief explanation of drawings]

FIGS. 1(a) to (e) are cross-sectional views showing a pattern forming method according to an embodiment of the present invention in the order of steps, and FIGS. 2 and 3 are for explaining the conventional lift-off method. FIG. 1-----1 Thin film

Claims (1)

[Claims] A thin film was selectively formed on a semiconductor substrate, a photoresist layer was then deposited on the entire surface, an opening was formed therein that was narrower than the width of the thin film, and the thin film was removed using the photoresist layer as a mask. 1. A method for forming a pattern of a semiconductor device, comprising: later forming a metal layer, then removing the metal layer on the photoresist layer together with the photoresist layer, and forming a metal pattern at the location where the thin film has been removed.